Mystery of 430,000-year-old murder at Sima de los Huesos
It is the ultimate cold case file - a death 430,000 years ago that may be the first confirmed murder in human history.
Scientists used modern forensic techniques to determine the victim was probably killed by two blows to the head before being tossed down a cave system shaft.
The truth of what occurred at the Sima de los Huesos (Pit of Bones) site in the Atapuerca Mountains, northern Spain, was revealed after researchers pieced together 52 fragments of a near-complete skull.
They discovered two holes close together in the skull, above the left eye, caused by two separate impacts from the same object following slightly different trajectories.
The injuries were inflicted around the time of the individual's death and were not consistent with an accidental fall down the 13-metre (42.6ft) deep vertical shaft. The Spanish and US-led international team said: "Given that either of the two traumatic events was likely lethal, the presence of multiple blows implies an intention to kill."